The drive train of a motor vehicle between the internal combustion engine and the driving wheels necessarily has certain elasticity, and therefore, in the event of a load change, undesirable vibrations may occur in the drive train. It is known to damp vibrations of this kind after a predetermined idle time has elapsed following a load change, by reducing the ignition angle of the internal combustion engine by a defined angle for a predetermined effective duration, after which the ignition angle is returned to the original value. This type of ignition angle control has a beneficial influence on the drive torque of the internal combustion engine, and thus damps the vibrations in the drive train which are excited by the load change. One disadvantage, however, of this method is that manufacturing tolerances, aging effects of the engine suspension, and the current transmission ratio during the load change are not taken into account. Thus, over the course of time, the suspension of the internal combustion engine becomes softer on account of aging effects, with the result that the tendency of the drive train to vibrate increases. Furthermore, in transmission engines, load changes have a greater effect in low gears than in high gears.
DE 42 32 204 A1, DE 42 22 298 A1, DE 40 13 943 C2, DE 40 09 792 A1 and U.S. Pat. No. 5,452,698 disclose methods for the damping of mechanical vibrations in the drive train of an internal combustion engine, in which the ignition angle adjustment takes place in a flexible way as a function of the operating state of the internal combustion engine, or as a function of the intensity of the vibration. A disadvantage of these methods, however, is that vibration suppression commences only when a vibration has already occurred in the drive train, since the rotational speed of the crank shaft is evaluated in order to determine a vibration in the drive train. Consequently, these methods make it possible to damp only vibrations which have already occurred in the drive train, whereas it is not possible, or is possible only to an unsatisfactory extent, to avoid a vibration occurring in the drive train.
Furthermore, DE 39 30 487 A1 discloses a method for the damping of mechanical vibrations in the drive train of an internal combustion engine, in which a fuel injection pulse width is detected, so that an acceleration operation can be detected even before the occurrence of mechanical vibrations in a drive train. The damping method known from this reference commences only when the measurement of the fuel injection pulse width announces an imminent acceleration operation, but the ignition angle adjustment takes place independently of the fuel injection pulse width and is fixed as a function of other variables. This method also has the disadvantage that the actual ignition angle adjustment, and consequently the damping action, are independent of the injection quantity, and thus there is no flexible quantitative adaption of the damping action to the injection quantity.
Finally, DE 37 17 368 C2 discloses a method for the damping of mechanical vibrations in the drive train of an internal combustion engine, in which the throttle valve position is detected, so that an imminent acceleration operation can be timely detected. In the event of an acceleration, the ignition angle is adjusted in a flexible way, with the duration of the ignition angle adjustment depending on the change in the throttle valve position, and consequently on the intensity of the imminent acceleration operation. This method has the disadvantage that only the duration of the ignition angle adjustment is dependent on the throttle valve position, and the adaption of the vibration damping to the intensity of the imminent acceleration operation takes place in an unsatisfactory manner.